Simon Prebble owned Scientific Demonstrations Ltd. and in 1967 they began to manufacture the first Newton’s Cradles. It is unknown who created the first one, but it is believed that it was an unknown Canadian scientist.
The Newton’s Cradle is a simple demonstration of physics. They are typically constructed with anywhere from three to five balls, all of the same weight and size. If one ball is pulled back and dropped, when it strikes the other balls its kinetic energy is transferred through all the other balls into the end ball, which then swings out. This works no matter how many balls you drop. This is purely due to the transfer of kinetic energy. Some kinetic energy transfers into each ball and leaves the cradle, which is why the balls will stop swinging if left for a while.
My experiment will test what happens if one of the balls in the middle of the cradle is replaced with a ball of a different size. I will test this by using a stopwatch and timing ten drops, using the sound made by the balls colliding as a guide. While doing this, I will also use a video camera to analyze the motion of the other balls in the cradle to determine if any changes in the energy transfer are occurring.
Use the following picture as a reference, so that as you read my data you know what i mean by some terms:
From left to right: Last Ball, off-center ball, center ball, off center ball, dropped ball.
This is how I will refer to the balls from here on.
Procedure
I first weighed one ball on the unmodified Newton's Cradle. I then weighed the ball that I was going to use in the experiment, which is slightly larger than the balls on the Newton's Cradle, and found that it weighed 66.55 grams while the balls on the Newton's Cradle weighed 44.75 grams. I then used electrical tape to attach fishing wire to the ball I would add to the cradle. Then, I did a control test without adding the ball, measuring 10 clicks and recording video. I then pulled the middle ball out and using tape attached the larger ball to the cradle and did another test. I then replaced the original ball, and moved the larger ball to the off-center position on the cradle, and did another test.
Results
Times for 10 clicks
Control- 3.53 seconds
Larger ball dead center- 3.31 secs
Larger ball off center- 3.32 secs
It seems that adding a ball very slightly drops the time it takes for 10 collisions to occur.
Upon analyzing the video data, I found that I might have dropped the balls from slightly different heights, despite my attempt to keep the height consistent. This could cause a change from test to test, and an increase to time.
I measured the velocities of the dropped ball, the middle ball, the off center ball, and the last ball. I used the highest velocity of each ball after the initial collision.
Maximum velocities
Control:
Dropped Ball- 2.111 f/s,
Last Ball- 1.907 f/s
Off center ball: .265 f/s
Off-center large ball:
Dropped ball- 1.309 f/s
Last ball- 1.149 f/s
Middle ball- .062 ft/s
Off center ball- .383 f/s
Large ball in center:
Dropped ball- 1.121 f/s
Last ball- .964 f/s
Off Center Ball- .294f/s
Middle Ball- .300 f/s
The following graphs show the velocities of the balls upon collision with the first ball. The graphs end after the second ball reconnects with the cradle after its swing.
This is the graph for the control test:
This is the graph for the off-center large ball test.
This is the graph for the Large ball in center test:
Conclusions
I found that there was a small difference in the velocities of the balls depending on where the larger ball was. The most noticeable difference, though, was the difference in the motion of the balls. With the control test, the middle balls did not move much at all, and remained fairly steady. The tests with a larger ball moved around much more. The test with the ball off center moved the most, and at points all five balls were moving at once.
I conclude that adding a slightly larger ball does affect the motion of the Newton's Cradle by slightly affecting the kinetic energy absorbed by each ball.
If one were to try to further test these results, I would suggest using larger and smaller balls than I used.
Table of Contents
Ball Size and the Newton's Cradle
MarcIntroduction
Simon Prebble owned Scientific Demonstrations Ltd. and in 1967 they began to manufacture the first Newton’s Cradles. It is unknown who created the first one, but it is believed that it was an unknown Canadian scientist.
The Newton’s Cradle is a simple demonstration of physics. They are typically constructed with anywhere from three to five balls, all of the same weight and size. If one ball is pulled back and dropped, when it strikes the other balls its kinetic energy is transferred through all the other balls into the end ball, which then swings out. This works no matter how many balls you drop. This is purely due to the transfer of kinetic energy. Some kinetic energy transfers into each ball and leaves the cradle, which is why the balls will stop swinging if left for a while.
My experiment will test what happens if one of the balls in the middle of the cradle is replaced with a ball of a different size. I will test this by using a stopwatch and timing ten drops, using the sound made by the balls colliding as a guide. While doing this, I will also use a video camera to analyze the motion of the other balls in the cradle to determine if any changes in the energy transfer are occurring.
Use the following picture as a reference, so that as you read my data you know what i mean by some terms:
From left to right: Last Ball, off-center ball, center ball, off center ball, dropped ball.
This is how I will refer to the balls from here on.
Procedure
I first weighed one ball on the unmodified Newton's Cradle. I then weighed the ball that I was going to use in the experiment, which is slightly larger than the balls on the Newton's Cradle, and found that it weighed 66.55 grams while the balls on the Newton's Cradle weighed 44.75 grams. I then used electrical tape to attach fishing wire to the ball I would add to the cradle. Then, I did a control test without adding the ball, measuring 10 clicks and recording video. I then pulled the middle ball out and using tape attached the larger ball to the cradle and did another test. I then replaced the original ball, and moved the larger ball to the off-center position on the cradle, and did another test.
Results
Times for 10 clicks
Control- 3.53 seconds
Larger ball dead center- 3.31 secs
Larger ball off center- 3.32 secs
It seems that adding a ball very slightly drops the time it takes for 10 collisions to occur.
Upon analyzing the video data, I found that I might have dropped the balls from slightly different heights, despite my attempt to keep the height consistent. This could cause a change from test to test, and an increase to time.
I measured the velocities of the dropped ball, the middle ball, the off center ball, and the last ball. I used the highest velocity of each ball after the initial collision.
Maximum velocities
Control:
Dropped Ball- 2.111 f/s,
Last Ball- 1.907 f/s
Off center ball: .265 f/s
Off-center large ball:
Dropped ball- 1.309 f/s
Last ball- 1.149 f/s
Middle ball- .062 ft/s
Off center ball- .383 f/s
Large ball in center:
Dropped ball- 1.121 f/s
Last ball- .964 f/s
Off Center Ball- .294f/s
Middle Ball- .300 f/s
The following graphs show the velocities of the balls upon collision with the first ball. The graphs end after the second ball reconnects with the cradle after its swing.
This is the graph for the control test:
This is the graph for the off-center large ball test.
This is the graph for the Large ball in center test:
Conclusions
I found that there was a small difference in the velocities of the balls depending on where the larger ball was. The most noticeable difference, though, was the difference in the motion of the balls. With the control test, the middle balls did not move much at all, and remained fairly steady. The tests with a larger ball moved around much more. The test with the ball off center moved the most, and at points all five balls were moving at once.
I conclude that adding a slightly larger ball does affect the motion of the Newton's Cradle by slightly affecting the kinetic energy absorbed by each ball.
If one were to try to further test these results, I would suggest using larger and smaller balls than I used.
References
http://en.wikipedia.org/wiki/Newton's_cradle
http://wordplay.blogs.nytimes.com/2010/12/06/numberplay-newtons-cradle/